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* https://www.linuxfromscratch.org/hints/downloads/files/boot-cd_easy.txt | |
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mkdir sources mv *patch *xz *gz *bz2 sources/ |
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= initramfs with static program = * https://www.kernel.org/doc/html/latest/filesystems/ramfs-rootfs-initramfs.html#contents-of-initramfs A good first step is to get initramfs to run a statically linked "hello world" program as init {{{#!highlight sh sudo apt install qemu-system cd /tmp wget https://saimei.ftp.acc.umu.se/debian-cd/current/amd64/iso-cd/debian-12.1.0-amd64-netinst.iso sudo mount -o loop /vagrant/debian-12.1.0-amd64-netinst.iso /mnt/iso # reuse isolinux from debian iso mkdir /tmp/debiancd mkdir /tmp/debiancd/isolinux mkdir /tmp/debiancd/install.amd cd /mnt/iso cp isolinux/isolinux.cfg isolinux/*c32 isolinux/menu.cfg isolinux/txt.cfg /tmp/debiancd/isolinux cp install.amd/initrd.gz install.amd/vmlinuz /tmp/debiancd/install.amd/ cp /mnt/iso/isolinux/isolinux.bin /tmp/debiancd/isolinux/ # hello.c cat > hello.c << EOF #include <stdio.h> #include <unistd.h> int main(int argc, char *argv[]) { printf("Hello world!\n"); sleep(999999999); } EOF gcc -static hello.c -o init echo init | cpio -o -H newc | gzip > test.cpio.gz cp test.cpio.gz debiancd/install.amd/test.cpio.gz cat > debiancd/isolinux/isolinux.cfg << EOF default bootcd prompt 1 timeout 40 label bootcd kernel /install.amd/vmlinuz append initrd=/install.amd/test.cpio.gz vga=788 EOF cd /tmp/ mkisofs -o /tmp/output2.iso -R -l -L -D -b isolinux/isolinux.bin -c isolinux/boot.cat -no-emul-boot -boot-load-size 4 -boot-info-table -V "LFS_$(date +%Y%m%d)" /tmp/debiancd/ rm /vagrant/output2.iso cp output2.iso /vagrant }}} qemu-system-x86_64 -kernel debiancd/install.amd/vmlinuz -initrd test.cpio.gz /dev/zero |
LinuxFromScratch
Linux From Scratch (LFS) is a project that provides you with step-by-step instructions for building your own custom Linux system, entirely from source code.
https://www.linuxfromscratch.org/lfs/downloads/stable/LFS-BOOK-11.3-NOCHUNKS.html
https://www.linuxfromscratch.org/hints/downloads/files/boot-cd_easy.txt
https://www.linuxfromscratch.org/lfs/downloads/stable/wget-list
List of the required downloads for LFS 11.3
initramfs with static program
https://www.kernel.org/doc/html/latest/filesystems/ramfs-rootfs-initramfs.html#contents-of-initramfs
A good first step is to get initramfs to run a statically linked "hello world" program as init
1 sudo apt install qemu-system
2
3 cd /tmp
4 wget https://saimei.ftp.acc.umu.se/debian-cd/current/amd64/iso-cd/debian-12.1.0-amd64-netinst.iso
5 sudo mount -o loop /vagrant/debian-12.1.0-amd64-netinst.iso /mnt/iso
6
7 # reuse isolinux from debian iso
8 mkdir /tmp/debiancd
9 mkdir /tmp/debiancd/isolinux
10 mkdir /tmp/debiancd/install.amd
11 cd /mnt/iso
12 cp isolinux/isolinux.cfg isolinux/*c32 isolinux/menu.cfg isolinux/txt.cfg /tmp/debiancd/isolinux
13 cp install.amd/initrd.gz install.amd/vmlinuz /tmp/debiancd/install.amd/
14 cp /mnt/iso/isolinux/isolinux.bin /tmp/debiancd/isolinux/
15
16 # hello.c
17 cat > hello.c << EOF
18 #include <stdio.h>
19 #include <unistd.h>
20
21 int main(int argc, char *argv[])
22 {
23 printf("Hello world!\n");
24 sleep(999999999);
25 }
26 EOF
27 gcc -static hello.c -o init
28 echo init | cpio -o -H newc | gzip > test.cpio.gz
29
30 cp test.cpio.gz debiancd/install.amd/test.cpio.gz
31
32 cat > debiancd/isolinux/isolinux.cfg << EOF
33 default bootcd
34 prompt 1
35 timeout 40
36
37 label bootcd
38 kernel /install.amd/vmlinuz
39 append initrd=/install.amd/test.cpio.gz vga=788
40 EOF
41
42 cd /tmp/
43 mkisofs -o /tmp/output2.iso -R -l -L -D -b isolinux/isolinux.bin -c isolinux/boot.cat -no-emul-boot -boot-load-size 4 -boot-info-table -V "LFS_$(date +%Y%m%d)" /tmp/debiancd/
44 rm /vagrant/output2.iso
45 cp output2.iso /vagrant
qemu-system-x86_64 -kernel debiancd/install.amd/vmlinuz -initrd test.cpio.gz /dev/zero